Field of the Invention
The present invention relates to an image forming apparatus, a control method therefor, and a storage medium storing a control program therefor, and in particular, relates to an image forming apparatus that uses a plurality of fixing devices by switching them according to a printing medium.
Description of the Related Art
In a field of production print, a large quantity of printing may be performed on special sheets other than plain paper using an image forming apparatus like a laser beam printer or a digital multifunctional peripheral device. Then, when printing on envelopes, an operator exchanges a normal fixing device used for printing on plain paper for an envelope-dedicated fixing device in order to prevent the fixing device from crinkling an envelope passed through, and starts printing.
An envelope-dedicated fixing device differs in materials of a pressure roller and a fixing belt and in fixing nip pressure from a normal fixing device. A normal fixing device is able to print on an envelope by changing fixing nip pressure and press speed. However, it is preferable to use an envelope-dedicated fixing device in order to print a large number of envelopes with higher quality at higher speed.
In production print, a large quantity of printing is often performed using a certain type of sheets. Accordingly, a large quantity of printing is performed using an envelope-dedicated fixing device in the case of printing on an envelope, and using a normal fixing device in place of the envelope-dedicated fixing device in the case of printing on another type of sheets. Furthermore, image processing parameters are changed according to the type of a fixing device with which the image forming apparatus is equipped. For example, there is a known method that stores gamma correction data used for adjusting density of a print image, the type of the fixing device at the time of generating image data, and the type of the sheet used in printing into a memory, and changes the image processing parameters at the time of printing (see Japanese Laid-Open Patent Publication (Kokai) No. 2013-088683 (JP 2013-088683A)).
Moreover, there is a known image forming apparatus that determines the type of a fixing device attached to the image forming apparatus by means of a photosensor etc., and displays a message, which shows that an envelope-dedicated fixing device is attached, on an operation screen when the determined type means the envelope-dedicated fixing device.
Furthermore, there is a known image forming apparatus that displays a warning message urging an operator to return the fixing mode to a normal mode after the last sheet is fixed in an envelope mode, when the current fixing mode is the envelope mode and the following image formation is not instructed, or when the sheet designated by the following image formation is not an envelope (see Japanese Laid-Open Patent Publication (Kokai) No. 2012-98518 (JP 2012-98518A)).
However, since the conventional image forming apparatus only determines whether the attached fixing device is a special fixing device (for example, an envelope-dedicated fixing device), it is difficult to manage a plurality of fixing devices of the same type. For example, even when a plurality of envelope-dedicated fixing devices are used for different uses, the message only shows that an envelope-dedicated fixing device is attached, which cannot support an operator.
Specifically, when an operator wants to use the fixing devices for different sizes of printing sheets or different size systems of sheets, a conventional image forming apparatus cannot attract operator's attention about the usage of an attached fixing device. As a result, the printout sheets that the operator wants may not be output.